Bolt for machine-guns.



C. H. SHEPARD.

BOLT FOR MACHINE GUNS.

APPLICATION FILED APR. 10. I918. 1,284,478. Patented Nov. 12, 1918.

Fig. 4.

I F g gm 4 W To all whom it may concern:

CHARLES H. SHEP RD, BBIDGEPOR'I, CONNECTICUT.

BOLT FUR MACHINE-GUNS.

specification of Letters Patent.

Patented Nov. as, i918.

.dpplication'nled April lfl, 1918. Serial No. 227,614.

Be it known that 1, CHARLES H. Sunr- ARD, a citizen of the United States, and resident of Bridgeport, in the county of Fairfield and State of Connecticut, have invented certain new and useful Improvements in Bolts for Machine-Guns, of which the following is a specification.

The object of the invention is to cheapen the manufacture and improve the construction of bolts such as are used in the type of niachine-gun recently adopted by the United States Army and known as the Browning gun, In these guns a reciprocating bolt carries a firing-pin longitudinally movable within'it, and this firing-pin has an offset, tapered firing-point, which in theact of firing projects through an offset, tapered firing-hole in the bolt at the forward end of the chamber in which the firing-pin works.

"The production of the offset, tapered hole in the bolt has been a matter of substantial diiiiculty and expense, owing to a preliminary operation which has heretofore been necessary, this operation being delicate and costly in its nature and of no benefit in the completed weapon, but merely for the purpose of affording room for the passage of the reaming tool which brings the initial parallel-sided hole to the desired taper. The operation in question is the formation of a side out in the firing-pin chamber of the bolt, inclining from a point intermediate the ends of the chamber to a sufficient depth at the forwardend to permit the reamer to act.

By my invention 1 do away with this troublesome step, by means of an altogether different operation, which is of exceedingly simple character and correspondingly insignificant expense, and the result of which is of permanent value in the gun. This step consists in making a transverse bore or drilling in such manner as to intersect the rear portion of the firing-hole, or the region corresponding thereto, producing an enlargement of sufficient size and suitable form to receive the broad basal portion of the firing-point. This crossbore eliminates the necessity of reaming out the back of the hole,

and all that remains is a slight reaming-out of the small forward part thereof, which can readily be accomplished without cutting into the side of the firing-pin chamber of the bolt.

In the accompanying drawings:

Figure l is a longitudinal section through the bolt and firing-pin'illustrating the invention;

Fig. 2 is, a cross-section on the line 2-2 of Fig. 1;

Fig. 3 is a perspective view of the forward end of the firing-pin;

Fig. 4 is a fragmentary longitudinal sectioi through the bolt as previously made; an

Fig. 5 is an enlarged fragmentary cross section through this construction;

The drawings represent the bolt 2 of a Browning gun. The relation of this bolt to parts of the weapon other than the firingpin 3 has not been illustrated because unnecessary to an understanding of the invention. As those familiar with this type of machine-gun are aware, the bolt is guided for longitudinal reciprocation, and in the operation of the gun vibrates back and forth. It contains a longitudinal chamber 4, fitted slidably by the firing-pin.

The firing-pin 3 is a hollow cylinder or rod, containing the spring chamber 5. In this chamber is a helical compression spring 6, introduced through the open front end of the firing-pin and confined between "a cross-pin 7 in the forward part of the firingpin and a vertical pin 8 secured in the bolt and passing through a slotted opening in the firing-pin. \Vhen the firing-pin is forced rearward in the bolt the spring has its compression increased and tends to drive the firing-pin forward. At the rear of the firing-pin is a catch shoulder 9 to engage a sear 10, which is actuated by a spring 11. The firing-pin is forced rearward in the bolt into engagement with the sear by a lever 12 pivoted at 13 in the bolt and adapted to engage at its upper arm with a relatively stationary part (not shown) as the bolt travels rearward. Release of the sear by means not shown permits the firing-pin to shoot forward.

14 is the offset firing-point, consisting of a forward projection from thebottom part of the wall of the firing-pin. .This firingpoint is large at the base, its greatest dimension being horizontal, and tapers to a small striking extremity. The outer and inner surfaces of the firing-point are convex and concave, respectively, being continuations of the outer and inner curvatures'of the pin.

The firing-point operates through a firinghole 15 extending through the front wall of the novel form of thishole and its method of production that the invention resides, the other features described being old.

Heretofore it has been customary to make the firing-hole by drilling-a larger hole part way through, from the inside and a smaller hole from the outside to meet it, and then reaming out this two-diameter hole'from the inside to the tapered form shown at l5" in Fig. 4. This reamed-out hole'was circular in all its cross-sections, and since its rear part hadto be wide enough to take in the greatest width of the base of the firing-point 14, it followed that its bottom are had to out below the bottom of the firing-pin chamber 4. This necessitated, as a preliminary, operation, the making of the sloping cut a in the bottom side of the chamber, which side out is difiicult and expensive as heretofore stated.

In my invention the rear part of the firing-hole Which receives the broad base of the firing-point is formed or is enlarged, as the case may be, by a portion of a small cross-bore 16, which is drilled in from one side of the bolt 2, terminating therein somewhat past the chamber-4. This cross-bore intersects the rear of the firing-hole or the axis thereof and also cuts into the front end of the chamber 4, and forms in effect a Wide and sufiiciently high entrance aflordin adequate clearance for the base of the ringpoint. V

The forward part 15 of the hole, which it will be understood already exists as a small drill-hole, is now reamed out to an appropriate taper, but this operation does not require any side out such as shown at a in Fig. .1-.

The advantages of my construction and procedure are fully set forth in the introductory part of the specification.

at I claim as new is:

1. In a firearm comprising a firing-pin having anoffset tapered point and aibolt chambered to receive the firing-pin and hav- 1 mg an offset firing-hole, a bolt characterized by a transverse bore intersecting the inner part of the firing-hole which receives the broad basal portion of the point.

2. In a ,firearm comprising a firing-pin having an oifset tapered point and a bolt chambered to receive the firing-pin. and hav ing an ofl'set firing-hole, a bolt character ized by 'a transverse bore intersecting the inner part of the firing-hole which receives the broad basal portion of the point, the portion of the firing-hole in front of said transverse bore being reamed out.

3. In a machine-gunhaving a'firing-pin. withan ofi'set tapered point, a part wherein said firings-pin operates having a longitudinal chani ber for the pin and an offset firinghole and characterized by a transverse bore forming an enlarged junction between the inner portion of the firinghole and the chamber, for the purpose set forth.

4. A part to constitute the bolt of a ma- 'chine-gun, sald part having a longitudinal chamber and an oflset firing-hole to receive a firing-pm having anofi'set tapered point, characterized by a transversebore intersecting the inner part of the firing-hole and of a size to afford clearance for the basal portion of the point and to permit the part of the hole in front ofsaid transverse .bore to cutting, into the side be reamed out without of the chamber.

In testimony whereof, I have name to this specification.

CHARLES H. SHEPARD.

signed my 

